There is a growing interest to better understand one or more parameters in selected bodies of water such as pools, lakes, rivers, and areas of the ocean. A body of water may contain many naturally-occurring elements including radionuclides, as well as elements generated by humans including the remnants of nuclear disasters and nuclear weapons testing and other contaminants.
The background level of radiation in water varies around the globe. The primary source of cesium-137, for example, has been atmospheric nuclear weapons testing in the 1950s and 1960s, but particular regions have experienced noticeable increases in radionuclides, also referred to as radioisotopes. The Irish Sea shows elevated levels of cesium-137 compared to large ocean basins as a result of radioactive releases from the Sellafield nuclear fuel reprocessing facility at Seacastle, UK. Levels in the Baltic and Black Seas are elevated due to fallout from the 1986 explosion and fire at the Chernobyl nuclear reactor. Fallout, runoff, and continued leaks from the Fukushima Dai-ichi nuclear power plant have added to the background level of radiation in the Pacific Ocean starting in 2011.
Interest has been shown in sampling, especially for water quality at local sites, at websites such as the “How radioactive is our ocean?” in “http://ourradioactiveocean.org” currently operated with the Center for Marine and Environmental Radiation at Woods Hole Oceanographic Institution. An interactive map with selected water-quality results is currently available at the “View Current Results” page at that website. In order to measure radionuclides or other water quality parameters on a larger special scale, a method for achieving faster collection of samples in situ is necessary.
Cesium-selective materials, typically fibers or resins such a resin beads, can be linked with KNiFC (potassium-nickel hexacyanoferrate (II)), or other transition metal ferrocyanide complexes to form materials that are sorbent at neutral pH and are selective for cesium-like elements. One specific example is a resin that incorporates active KNiFC associated with inorganic ion exchangers embedded with modified polyacrylonitrile (PAN) as a binding matrix, as described by Sebesta in “Composite sorbents of inorganic ion-exchangers and polyacrylonitrile binding matrix”, J. Radioanalytical and Nuclear Chem., Vol. 220, No. 1, 77-88 (1997). Copper ferrocyanide has also been used for cesium sorption in association with fibers, as discussed by Buesseler et al. in “Determination of Fission-Products and Actinides in the Black Sea Following the Chernobyl Accident”, J. Radioanalytical and Nuclear Chem., Vol. 138, No. 3, 33-47 (1990). Sampling and analysis of cesium near Japan is described by Buesseler et al. in “Fukusima-derived radionuclides in the ocean and biota off Japan”, PNAS Early Edition, www.pnas.org/cgi/doi/10.1073/pnas.1120794109, 1-5 and “Supporting Information” 1-7 (2012).
Use of sorbents having different properties to determine the concentration of dissolved thorium is discussed by Hartman and Buesseler in “Adsorbers for In-Situ Collection and At-Sea Gamma Analysis of Dissolved Thorium-234 in Seawater”, WHOI Technical Report, WHOI-94-15 (1994). Impregnation of polypropylene cartridges with MnO2 is described in the Appendix.
Most sampling and measurement of radionuclides, also referred to as radioisotopes, and other elements requires known volumes of water. Water itself is heavy, and transporting quantities of water to be analyzed is awkward and can be expensive.
It is therefore desirable to have portable, preferably wearable, sampling devices that can be utilized by a wide variety of people to monitor selected parameters in water, in air, or in another amorphous medium.